Modern batteries may be good, but so far as I know (not much) they still have problems.
These are likely to be a short life if the battery is very rapidly discharged and charged,
and they are heavy. The mass means that they cannot be placed on the roof - where they
could be easily replaced, they must be placed lower, and preferably in some sort of tray
that can be easily slid out and in when they are replaced. This means that there must be
substantial 'gaps' in the shell to allow this.

Add in cost, both initial and to replace, and add in a substantial recharge time if they
cannot be easily recharged en route.

Compare them with supercapacitors - these are designed for very quick discharge and
recharge. They are believed to have a long life time - SFAIK none of the original
supercaps have had to be replaced because they have worn out, more likely replaced for
test and examination. They are also believed to be heavy, but the size could be varied
from one massive unit to several small units as space and structure permit. They can be
more easily recharged en route as charging is fast and does not destroy the unit, which
could be either from an overhead collector or a short rail as per APS. Even though they
are heavy, I believe they are normally placed on the roof.

For buses, it seems that design is going the battery route - perhaps the familiarity of
the car battery makes these seem better than the "new-fangled" supercap.

With trams, I would suggest that supercaps is the way to go.

Query, does anyone know if they develop much heat in use? Are they placed on the roof so
as to remove the heat easily, or is it just that there is space there? If there is not
too much heat developed, I would suggest that consideration be given to using a number of
small units, sufficiently small as to be placed under the seats. This uses what is really
wasted space, and also lowers the CG of the tram and reduces the strengthening needed for
their carriage in the roof.

If recharge is from a rail, then I would suggest that the rail or the overhead is as long
as the tram. At a stop, as soon as the front pick up contacts the rail or the overhead
then braking energy can be returned to a roadside supercap, and when accelerating power
can be drawn from the rail/overhead as long as the rear pick up is still in contact with
it. From v squared = 2 a s, and taking a as 1.3 and s as 60, we get v = 12.5 m/s = 41
ft/sec. This is, if my maths is correct, almost 28 mph. This covers a very large chunk
of the desired acceleration and braking distance, and reduces the amount of energy to be
stored to cover the rest of the acceleration period. (Does nothing for the energy
consumed in a/c, heating and lights, however.)

For info, I came across this, which may or may not help:
http://energyandcarbon.com/lithium-ion-batteries-versus-supercapacitor/

Any comments, please?

Regards

Dudley Horscroft

-----Original Message-----
From:TramsDownUnder@... [mailto:TramsDownUnder@yahoogroups.com]
Sent: Monday, 16 October 2017 8:50 PM
To:TramsDownUnder@...
Subject: Re: [TramsDownUnder] Electric bus - partial trolleybus

The Plzen Elektrobus project is still going as far as I know. It's basically live,
in-service development testing and is one of the European projects under the Zeeus
program. The state of play in the operation on this route in 2016 is well-summarised here:

https://www.skoda.cz/en/skoda-perun-electric-buses-celebrate-their-first-year-of-operation
-in-pilsen/

It's running the service past where I lived in Plzen, pity I missed it by a couple of
years. It would have been an interesting comparison with the Chinese BYD buses in Sydney.

The Plzen buses are completely uncompromised fully low-floor normal citybuses. The BYD bus
interiors are compromised to hell to fit lots of batteries on board to give it the range
(running continuously, so flash recharges aren't possible). As a result its a terrible
crowd-handler even with its three doors.

The magic trick is to get the range without compromising the functionality.

There's a pair of new Australian-developed, fully low-floor 12 metre Bustech battery buses
about to make an appearance in Adelaide. It's looking basically OK from photos I've seen,
but seems to have sacrificed a row of seats at the back to accommodate batteries. Make a
note to ride on them when they start running Mark and you'll be able to compare with the
Skoda buses.

Tony P

------------------------------------
Posted by:prescottt@...
------------------------------------

------------------------------------

Yahoo Groups Links